Sometimes you just have to know when to stop…

When you tow a trailer it is extremely important to be quite familiar with the distance necessary to be able to stop your rig. This sounds very basic, but it is more complex than driving your tow vehicle alone… you have to consider many factors, including the slope of the road, the loaded weight of the trailer and tow vehicle, road conditions, and more - all of these factors can dramatically affect your ability to stop the trailer, while keeping the rig under full control. The brakes of your tow vehicle are not designed to stop both the tow vehicle and a trailer, so the proper synchronization of trailer brakes with tow vehicle brakes is essential to safety and overall handling characteristics of the combination. The tow vehicle brakes are designed to stop only the GVW (Gross Vehicle Weight) of the car or truck, not the GCW (Gross Combined Weight) which is the loaded weight of the tow vehicle plus the weight of the trailer or fifth wheel.
            Over the years, many auxiliary aftermarket brake controllers have been available for RV use. The first design was a simple hydraulic controller that was connected by a certified brake mechanic into the steel brake line at the master cylinder. When you pushed on the brake pedal, the pressure in the line increased and forced a piston to push a piece of spring metal bar to short out a coil of resistance wire in the control unit. As the resistance became lower more current was allowed to flow to the trailer brakes. This was a simple, low cost, true proportional braking system. The harder you pushed on the brake pedal, the greater the current flow to the trailer brakes. While older tow vehicles may still operate with these controllers, this type of brake control system is no longer sold. With the addition of modern ABS braking systems in cars and trucks, you are not allowed to connect anything into the hydraulic brake system of the tow vehicle as it would displace a certain amount of brake fluid, causing erratic operation of the new brake systems.
            Owners of fleets of rental trailers started using a brake controller system that did not have to be mounted in the tow vehicle, but could be installed on the trailer itself. (This was great for companies like U-Haul). This brake control system operated on the principle that the longer you held your foot on the brake pedal, the more braking you required. This was a time-actuated system that ramped up the current to the trailer brakes. Even if you only required a small amount of braking, for example as you lightly touched the brake pedal going down a long hill, you still got the same amount of maximum current going to the trailer. The maximum current value was determined by a manual slide control on the side of the controller. To prevent the brakes from coming on too hard, you had to keep lifting your foot off the brake pedal so that the controller could reset to a lower value. This was fine for small cargo trailers, but not the optimum system for travel trailers and fifth wheels. The other problem was that if you needed to “throw out the anchor” for a quick stop, the maximum amount of current was not available until the controller ramped up after about three to five seconds. When you were traveling at 88 feet per second, this meant that you might not stop in time to avoid an accident.
            The inertial type brake controller was designed with an internal pendulum that broke a beam of light as the tow vehicle slowed down. The harder you decelerated, the more light was blocked from the photocell and therefore more current was sent to the trailer brakes. Before any trailer braking occurred, the tow vehicle had to start slowing down using its own brakes, which triggered the trailer brakes to be energized. There were inherent quirks with this system. If you were travelling downhill but not slowing down, the pendulum was still in a forward position, blocking light to the photocell. So if you touched the brake pedal slightly, the electronics received a signal that you needed more current than necessary. An improved version of this type of controller was developed that included an aircraft-type cable that connected the controller to the arm of the brake pedal. When you pushed on the brake pedal, you got an instant flow of current to the trailer brakes. This required that the cable be properly adjusted during installation and sometimes re-adjusted at a later date for proper operation.
            The accelerometer type brake controller also had a pendulum, but with a magnet on the end that swung past a coil of wire. Current to the brakes was only applied when there was movement of the magnet across the coil. If the tow vehicle was not decelerating, the magnet hung still over the coil and no current was developed in the coil. With this style of brake control, if you were going downhill before you touched the brake pedal it did not matter, as there was no movement of the magnet at the end of the pendulum relative to the coil position. A suitable amount of current would be sent to the trailer brakes depending upon how fast the pendulum moved, not by how far it moved. This has been one of the preferred brake control technologies in recent years. Both the accelerometer and the light actuated models could be installed by any good mechanic – they did not have to be installed by a certified auto mechanic as they did not connect into the hydraulic ABS brake system of the tow vehicle, but they did need to have the pendulum adjusted by turning a wheel on the side of the control unit so that when the vehicle was sitting still, the pendulum hung straight down. A normal brake control unit needs the gain to be set higher for stops from highway speeds than the setting required for stops from city traffic speed.
            Each of these trailer brake controllers had some drawbacks, and the quest for perfect braking control over the trailer brakes, especially at different speeds, continued. This year, on our 2008 Jeep Liberty, I will be using a new style trailer brake controller that is more computerized for proper braking control. Manufactured by Hensley Manufacturing to complement their full line of trailer towing products, it has been designed to operate with either standard magnetic brakes or the newer electric over hydraulic disc brakes. It automatically determines whether the trailer has brakes on one, two or three axles. This new design does not rely on a pendulum - instead it uses a solid-state gyroscope sensor to detect deceleration. This sensor will detect acceleration, deceleration, cornering, whether you are going uphill or down. Since you don’t normally put your foot on the brake pedal going uphill, the sensing unit is inactive at that time.
            There are two models available, The “True Control Gold” with a digital screen readable as words, and a slightly lower cost model with a row of lights to indicate the amount of braking. These units do not need to be readjusted for stops from different speeds. There are no adjustments for gain or leveling on the controller. Just a manual plunger-style lever on the left side to allow you to adjust the brakes of the trailer for normal stopping conditions, not for manual application of the brakes to correct trailer sway. (Hensley has excellent hitches for eliminating trailer sway before it starts). There are three touch buttons on the front that allow you to calibrate the unit after installation. Hensley provides a chart to allow you to adjust the unit for tow vehicle weight and trailer weight to achieve the desired braking intensity. Our Liberty weighed in at 4200 pounds and was capable of towing 5000 pounds of trailer, so we set the system for a value of “10". The setting can be changed from a “2" for a heavy tow vehicle with a light trailer up to as much as an “18" for a heavy 10,000 pound tow vehicle and an 18,000 pound trailer. Touch the “Up” or “Down” buttons until the desired configuration is reached.
            Next press the “ENTER” key (left arrow) until the “SCREEN OFF DELAY” shows on the screen. This delay allows you to set the time the screen is off from 30 minutes to seven hours to conserve electricity when it is not needed. Even though the screen is “OFF”, the controller is still working. The screen allows you to see the voltage to the brakes, the total braking amperes, and the percentage of braking being used.
            In discussion with drivers who have used the unit, I found that setting the controller to an “11" instead of “10" provided more aggressive braking than some prefer, but without the jerking that is normally felt at slower speeds with other controllers. They have said that the braking is smooth at both high speed and low speed stops.
            I am looking forward to an actual test with our new Liberty- so far it only has 400 km on the odometer as we just took delivery. I often suggest to RV’ers that they put about 1000 km on their new tow vehicle before actually towing anything. This allows the gears in the transmission and axles to wear-in without developing a glaze from the added load - that can cause a humming noise.